This invention relates to a technique for protecting information from unauthorized reproduction and, more particularly, to a security, information document having a hidden message which becomes visible when the document is reproduced, thereby indicating that the copy of the document is unauthorized.
The problem of unauthorized reproduction of information is widespread. Documents which contain information which is copyrighted, proprietary, or confidential are often reproduced without proper authorization. Attempts have been made to stop this unauthorized reproduction by adding identifying marks to the original documents. However, these attempts have been unsuccessful because the identifying marks are easily removed from the copies using a razor blade, correction fluid, erasure, or other means. The copies can then be distributed with no clear indication that they emanate from a particular source, that the copies are not authorized, or that the possessor may have no right to have the information.
Therefore, there is a need for a security, information document which provides protection from unauthorized reproduction of the document, and which provides an indication of the source of the document.